Hereditary Nonpolyposis Colorectal Cancer (HNPCC)/Lynch Syndrome: Surveillance and Diagnostic strategies

Introduction: Hereditary nonpolyposis colorectal cancer (HNPCC, Lynch syndrome) is an autosomal dominant genetic disease. The disease is caused by a mutation in one of four genes of the DNA mismatch repair system and increases the risk for various cancers, especially the uterine and colon cancers. The prevalence of this disease in the general population is about 1 in 500 and it causes about 2-3% of colorectal cancers. Lynch syndrome is diagnosed in two stages: 1) the person is suspected of having the disease (because a patient is unusually diagnosed with cancer at a young age), and 2) evidence of incomplete repair defect is seen in the tumor tissue (microsatellite instability). The detection of a pathogenic mutation confirms the diagnosis in these patients and enables predictive testing for other family members. Diagnostic evaluation of Lynch syndrome should be performed with appropriate genetic counseling. Systemic colonoscopy surveillance could identify colon cancers at an earlier stage before patients present clinical symptoms. Conclusion: Although many studies have been done, but the benefits of an individualized, risk-adapted surveillance strategy are still unclear. Until this is identified, Lynch syndrome patients and healthy carriers with causative mutations should be monitored by annual colonoscopy and annual gynecological examination (for women).